1. Field of the Invention
The present invention relates to a passenger protecting system for an automotive vehicle, the system including passenger protecting devices, such as airbags or seatbelt pretensioners, which are actuated upon detection of a collision.
2. Description of Related Art
A passenger protecting system having seat sensors for detecting passengers sitting thereon is disclosed in JPA-2002-200963. In this system, whether or not a passenger occupies a seat is detected by a seat sensor. A passenger protecting device for the particular seat which is not occupied is not actuated even when a collision is detected. Passenger protecting devices for other seats which are occupied are actuated upon detection of a collision. The passenger protecting system disclosed therein includes a main control unit, a safeguard control unit and a driving IC (a driving integrated circuit.
The main control unit determines switching elements for the protecting devices corresponding to the unoccupied seats based on signals from the seat sensors. Information regarding such switching elements not to be actuated upon detection of a collision is sent to the driving IC and to the safeguard control unit as well. The safeguard control unit also determines, independently from the main control unit, the switching elements not to be actuated upon detection of a collision. Only the switching elements indicated by both of the main and safeguard control units as those not to be actuated are finally selected as the switching elements not to be actuated. In this manner, the passenger protecting system disclosed in JP-A-2002-200963 is able to select the switching elements not to be actuated upon detection of a collision without using a hardware (such as MOSFET switches) disposed outside the passenger protecting system.
In the conventional passenger protecting system described above, however, the following problem is involved. That is, the passenger protecting devices corresponding to seats other than the unoccupied seats are all actuated regardless of types of collisions (a front collision, a right side collision or a left side collision). To eliminate this problem, a passenger protecting system in which the switching elements are selected according to types of collision has been proposed. This system will be briefly explained below with reference to FIG. 4.
The passenger protecting system 100 disclosed in FIG. 4 is mainly composed of a main control unit 101, a safeguard control unit 102 and a driving IC 103. The main control unit 101 includes a main detecting circuit 104 and a main driving signal generating circuit 105. Similarly, the safeguard control unit 102 includes a safeguard detecting circuit 106 and a safeguard driving signal generating circuit 107. The driving IC 103 includes an input interface 108 for main driving signals, another input interface 109 for safeguard driving signals, six main switching elements 110 and six safeguard switching elements 111. Each main switching element 110 is connected in series to each safeguard switching element 111 through a wire L100.
Operation of the passenger protecting system 100 will be briefly explained, taking a front collision as an example. Acceleration signals at a front collision are fed to the main detecting circuit 104 from main acceleration sensors (not shown in FIG. 4). The main detecting circuit 104 detects a type of collision based on the acceleration signals (a front collision is detected in this example). A signal 113 indicating a front collision is fed to an AND-gate 114. In the main driving signal generating circuit 105, a group of register channels 115 for a front collision are pre-programmed. In this particular example, register channels CH1, CH2, CH3 and CH4 are pre-programmed as the register channels for the front collision. Similarly, a register channel CH5 and a register channel CH6 are pre-programmed as register channels for a right side collision and for a left side collision, respectively.
Both the signal 113 indicating a front collision and the register channels 115 are fed to the AND-gate 114. The AND-gate 114 outputs main driving signals to register channels CH1–CH4 in the main input interface 108. Four main switching elements 110 corresponding to the register channels CH1–CH4, respectively, are driven.
The safeguard switching elements 111 are driven by the safeguard control unit 102 in the similar manner as described above. Signals from safeguard acceleration sensors (not shown in FIG. 4) are fed to the safeguard detection circuit 106. A signal 116 indicating a front collision and pre-programmed register channels 118 (i.e., CH1–CH4) are fed to an AND-gate 117. The AND-gate 117 outputs safeguard driving signals to register channels CH1–CH4 of the safeguard input interface 109. Four safeguard switching elements 111 corresponding to the register channels CH1–CH4, respectively, are driven by the safeguard driving signals.
When both of the main switching elements 110 and the safeguard switching elements 111 are driven, current flows through the wires L100 corresponding to CH1–CH4. Thus, actuators for the passenger protecting devices, such as airbags or seatbelt pretensioners, corresponding to the register channels CH1–CH4 are actuated.
The register channels CH1–CH6 can be allocated to respective passenger protecting devices in various ways. Three variations are shown in FIG. 5. In variation 1, for example, a register channel CH1 is allocated to an airbag positioned in front of a driver, CH2 to an airbag positioned in front of an assistant, CH3 to a seatbelt pretensioner for a driver, CH4 to a seatbelt pretensioner for an assistant, CH5 to a side airbag for a driver, and CH6 to a side airbag for an assistant. The allocation of register channels is pre-programmed both in the main driving signal generating circuit 105 and in the safeguard driving signal generating circuit 107.
The allocation of the register channels is not always the same, but it varies according to types of vehicles. Therefore, the allocation of the register channels has to be programmed for each vehicle type. Therefore, it has been difficult to use the main control unit 101 and the safeguard control unit 102 commonly to all types of vehicles. Also, it is required to tune-up program details in the main control unit 101, such as algorithm for detecting types of collision or detection criteria, according to specifications (such as a body shape, a body rigidity or a distance from an airbag to a driver) of each vehicle type. On the other hand, the safeguard unit 102 can be commonly used to various vehicle types except for the allocation of the register channels mentioned above. Therefore, if the programming of the register channel allocation in the safeguard driving signal generating circuit 107 is eliminated, the safeguard control unit 102 will be commonly used to most types of vehicles.